Molecular Characteristics and Gelling Properties of the Carrageenan Family, 1. Preparation of Novel Carrageenans and their Dilute Solution Properties

Abstract

The carrageenans are a family of sulfated polysaccharides extracted from red seaweed, and are conventionally classified into three major groups as κ-, ι- and λ-carrageenan according to the maximum number (1, 2 and 3, respectively) of sulfate groups per disaccharide repeating unit in corresponding ideal structures. β- and θ-carrageenan (not available in nature) possessing none and two sulfate groups per repeating unit, respectively, were prepared from κ- and λ-carrageenan by desulfonation. Here the aqueous solutions of κ-, ι-, β- and θ-carrageenans undergo the thermoreversible gelation by lowering temperature, whereas the aqueous solution of λ-carrageenan forms no gel.Light scattering and small-angle X-ray scattering were observed from the aqueous solution of κ-, ι-, λ-, β- and θ-carrageenans, and the results were analyzed conventionally and by adapting the molecular model in order to elucidate the effect of sulfate groups and anhydrous residue on the conformational characteristics of carrageenans.